The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As an alternative to the internal combustion engine (ICE), automotive manufacturers have developed hybrid powertrains that include both an electric machine and an internal combustion engine. During operation, hybrid powertrains use one or both of the power sources to improve efficiency.
Hybrid electric vehicles (HEVs) use either a parallel drivetrain configuration or a series drivetrain configuration. In the parallel HEV, the electric machine works in parallel with the ICE to combine the power and range advantages of the ICE with the efficiency and the electrical regeneration capability of the electric machine. In the series HEV, the ICE drives an alternator to produce electricity for the electric machine, which drives a transaxle. This allows the electric machine to assume some of the power responsibilities of the ICE, thereby permitting the use of a smaller and more efficient ICE.
One drawback to either configuration is that the ICE does not provide a constant, smooth, level of torque. Pulses in torque, inherent to ICEs, are referred to as torsional vibration. The torsional vibration can be due to combustion forces and/or hardware used in the engine design. The amplitude of these vibrations can have adverse effects at different speeds and loads depending on the engine configuration. In some applications, as the load demand is increased, the torsional vibration increases to levels that can produce noise and vibration levels that impact drivability. In other applications, cold ambient air conditions during startup induce torsional vibration which can be perceived as a “rattle.” Such conditions are undesirable.